Tackifier resins are commonly made by polymerizing 2-methyl-2-butene and piperylene with additional unsaturated hydrocarbons that contain from about 4 to about 18 carbon atoms. Such tackifier resins are widely utilized in manufacturing pressure sensitive and hot melt adhesives. Pressure sensitive adhesives are used in tapes, labels, adhesive bandages, glue traps for rats and mice, and numerous additional applications. Hot melt adhesives are employed in carton closures, book bindings, film lamination, tires, labels, tapes, packaging, and a wide variety of other products.
Tackifier resins based on hydrocarbon monomers that contain 5 carbon atoms (C5 hydrocarbons) offer unique characteristics that allow them to be used in applications where most other hydrocarbon resins do not adequately perform. Their light color, high tack properties, low specific gravity, oxidative stability and day-to-day consistency of properties make them an excellent choice for use in pressure sensitive adhesives. Pressure sensitive adhesives of this type are normally made by blending the C5 hydrocarbon tackifier resin with a rubbery polymer, such as natural rubber, butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, or a stereo specific polymer of a diene monomer, such as butadiene or isoprene. U.S. Pat. No. 3,846,352 describes pressure sensitive adhesive compositions of this type.
U.S. Pat. No. 4,060,503 discloses a rubber, xcex1-methylstyrene-modified piperylene/2-methyl-2-butene resin adhesive composition which comprises an admixture of (1) about 100 parts by weight of a rubber comprised of at least one of natural rubber, synthetic cis-1,4-polyisoprene elastomer, and an unvulcanized elastomeric styrene/isoprene block copolymer having the general configuration A-B-A wherein each A is an independently selected nonelastomeric styrene polymer block having an average molecular weight of about 2,000 to about 100,000 and a glass transition temperature above about 25xc2x0 C., the total block A content being from about 10 to about 50 percent by weight of the copolymer, and B is an elastomeric conjugated diene block of polyisoprene having an average molecular weight from about 25,000 to about 1,000,000 and a glass transition temperature below about 10xc2x0 C., said copolymer having a tensile strength at 25xc2x0 C. in excess of about 200 pounds per square inch, and (2) about 60 to about 140 parts by weight of a compatible piperylene/2-methyl-2-butene type, thermoplastic tackifying resin, modified with a minor amount of xcex1-methylstyrene containing carbon-to-carbon unsaturation therein and having a softening point in the range of about 80xc2x0 C. to about 105xc2x0 C. prepared by the method which comprises reacting in the presence of an aliphatic hydrocarbon solvent and a catalyst selected from at least one of aluminum chloride and ethylaluminum dichloride, a monomer mixture consisting of about 92 to about 99 weight percent of a diolefin/olefin mixture of a weight ratio in the range of about 0.6/1 to about 1.4/1 and, correspondingly, about 8 to about 1 weight percent xcex1-methylstyrene, where said diolefin is at least about 95 weight percent piperylene and said olefin is 2-methyl-2-butene; wherein said diolefin is optionally modified by containing up to about 5 weight percent isoprene and wherein said monomer mixture is optionally modified by containing up to about 10 weight percent of at least one monomer selected from the group consisting of piperylene dimers, piperylene trimers, 2-methyl-1-butene, 2-methyl-2-pentene, 2-methyl-1-pentene, 2,3-dimethyl-1-butene, 2,3-dimethyl-2-butene, 2-methyl-2-pentene, cyclopentene and 1,3-cyclopentadiene.
U.S. Pat. No. 4,288,567 discloses an adhesive composition which comprises an admixture of an unvulcanized block polymer product and a compatible tackifier resin therefor prepared by the method which comprises (A) mixing (1) 100 parts by weight of a solution polymerizate comprised of 100 parts by weight of an unvulcanized block styrene/isoprene polymer product with an overall styrene polymer content in the range of about 10 to 35 weight percent and its polymerization solvent in the range of about 300 to about 1100 parts by weight with (2) about 50 to about 200 parts by weight of a solution polymerizate comprised of 100 parts by weight of a tackifying resin for said block polymer product and its polymerization solvent in the range of about 25 to about 1100 parts by weight and (B) removing said solvent from the prepared mixture prior to its application as an adhesive; wherein the total of said polymerization solvents is a solvent for the combination of said block polymer and said resin; wherein said block polymer polymerizate is produced by the process of contacting isoprene and a suitable amount of divinylbenzene under solution polymerization conditions with a polystyryllithium catalyst, said amount of divinylbenzene being from about 0.5/1 to about 10/1 moles of divinylbenzene per mole of active lithium catalyst; and wherein said tackifier resin polymerizate is prepared by copolymerizing in the presence of a catalyst selected from the group consisting of aluminum chloride, boron trifluoride and boron trifluoride etherate, a mixture of piperylene and at least one olefin containing 4-6 carbon atoms in a diolefin/olefin mole ratio in the range of about 0.6/1 to about 2.5/1, optionally modified by copolymerizing about 5 to about 20 weight percent, based on the total monomers, of at least one additional monomer selected from alpha-methylstyrene and di-cyclopentadiene in which the resin itself has a softening point in the range of about 50xc2x0 C. to about 150xc2x0 C.
U.S. Pat. No. 4,172,860 discloses an adhesive composition comprises an admixture of (A) 100 parts by weight of an unvulcanized branched, thermoplastic block polymer product produced by the process consisting essentially of contacting a diolefin selected from the group consisting of at least one of isoprene and 1,3-butadiene premixed with a suitable amount of divinylbenzene, under solution polymerization conditions with a polystyryl lithium catalyst, said amount of divinylbenzene being from about 0.5/1 to about 10/1 moles of divinylbenzene per mole of active lithium catalyst to form said thermoplastic block polymer that is essentially non-gel and has the divinylbenzene coupling agent attached to the diolefinic portion of the block polymer, and (B) about 50 to about 150 parts by weight tackifier therefor; where said tackifier is a resin having a softening point in the range of about 50xc2x0 C. to about 150xc2x0 C. and is selected from at least one of terpene resins and synthetic hydrocarbon resins derived essentially as diolefin/olefin copolymers prepared by polymerizing the monomers in the presence of a catalyst selected from aluminum chloride or boron trifluoride or boron trifluoride etherate; and where, in said block copolymer, the polystyrene block molecular weight is in the range of about 8,000 to about 45,000, the polydiolefin block has a molecular weight in the range of about 10,000 to about 100,000, ignoring the divinylbenzene effect, with the overall styrene content in the block copolymer being in the range of 10 to 35 weight percent.
U.S. Pat. No. 3,577,398 is based upon the finding that a mixture of piperylene and 2-methyl-2-butene can be polymerized in the presence of a metal halide catalyst, such as aluminum chloride or stannic chloride, to form a tackifier resin that is useful in commercial applications. U.S. Pat. No. 3,577,398 specifically discloses a polymeric resinous composition comprising from about 40 to about 80 weight percent units derived from piperylene and from about 20 to about 60 weight percent units derived from 2-methyl-2-butene, wherein the resinous composition has a softening point that is within the range of about 80xc2x0 C. to about 110xc2x0 C. U.S. Pat. No. 3,577,398 indicates that the polymeric resinous composition can be modified by having up to about 25 weight percent units derived from certain other unsaturated hydrocarbons. The polymeric resinous composition is prepared by polymerizing a mixture comprising from about 20 to about 75 weight percent piperylene and from about 25 to about 80 weight percent of 2-methyl-2-butene in the presence of an anhydrous metal halide selected from aluminum chloride and stannic chloride.
U.S. Pat. No. 3,784,530 and U.S. Pat. No. 3,846,353 disclose a resinous material that is particularly useful as a tackifier for rubbery butadiene-styrene copolymers that has a softening point in the range of 60xc2x0 C. to about 110xc2x0 C. that is prepared by polymerizing piperylene, 2-methyl-2-butene, dicyclopentadiene, and xcex1-methylstyrene in the presence of a catalyst selected from the group consisting of aluminum chloride and ethyl aluminum dichloride and a solvent selected from aliphatic and aromatic hydrocarbons.
This invention is based upon the unexpected discovery that the reactivity of the most important monomers commonly used in synthesizing tackifier resins with aluminum halide catalysts can be enhanced by conducting the polymerization in the presence of an allylic halide. For instance, the conversions of 2-methyl-2-butene, cis-piperylene, and cyclopentene that are attained in polymerizations that are catalyzed with aluminum halide catalysts are increased by conducting the polymerization in the presence of an allylic halide, such as allyl chloride. Increased conversion is of great commercial importance because it leads to reduced cost that is attributable an increased level of efficiency and reactor capacity. The increased conversion of expensive monomers used in making the tackifier resin is of particular benefit. The implementation of this invention also reaps significant environmental benefits in that a greater quantity of monomers are consumed by the polymerization reaction which accordingly leads to the need for disposal of a lower volume of unreacted monomers.
The present invention more specifically discloses a process for synthesizing a resin having characteristics that make it particularly useful as a tackifier resin, said process comprising the polymerization of an unsaturated hydrocarbon monomer mixture in the presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms, and wherein said process is conducted in the absence of tantalum compounds.
The subject invention further reveals a process for synthesizing a resin having characteristics that make it particularly useful as a tackifier resin, said process comprising the polymerization of an unsaturated hydrocarbon monomer mixture in the presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of 2-methyl-2-butene, cis-piperylene, trans-piperylene, cyclopentene, and additional unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms.
In the process of polymerizing an unsaturated hydrocarbon monomer utilizing an aluminum halide catalyst, the present invention generally discloses the improvement which comprises conducting the polymerization in the presence of an allylic halide, wherein said process is conducted in the absence of tantalum compounds.
The process of this invention is normally conducted in the absence of tantalum compounds, such as tantalum halides and tantalum oxyhalides including TaCl3, TaCl4, TaCl3, TaCl2, TaOCl3, TaBr5, TaOBr3, and TaI5. Other tantalum compounds that are normally avoided include salts of tantalum with strong mineral acids, aliphatic and aromatic carboxylic acids, and its alcoholates and xcex2-keto-enolates, for example, tantalum ethylate and tantalum acetyl acetonates.
In some cases it is desirable to hydrogenate the tackifier resin to reduce the level of yellow color and undesirable odors that may be present. In high-end applications it is particularly desirable for the tackifier resin to be hydrogenated since hydrogenation can be used to reduce or eliminate these undesirable characteristics without having an adverse effect on the softening point, molecular weight or the aromaticity of the resin. Palladium on alumina catalyst systems are particularly advantageous for this purpose since they have proven to offer high activity and can be used under mild reaction conditions, such as low reaction temperature and pressure.
The present invention also reveals a process for synthesizing a hydrogenated resin having characteristics that make it particularly useful as a tackifier resin having low odor and low color characteristics, said process comprising the steps of (1) polymerization of an unsaturated hydrocarbon monomer mixture in the presence of aluminum halide and an allylic halide to produce an unsaturated resin, wherein the unsaturated hydrocarbon monomer mixture is comprised of unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms, and wherein said process is conducted in the absence of tantalum compounds; and (2) hydrogenating the unsaturated resin in the presence of a palladium on alumina catalyst system at a temperature which is within the range of about 120xc2x0 C. to about 240xc2x0 C. to produce the hydrogenated resin.